The present invention relates to a radar speedometer which is for use on a moving vehicle such as an automobile or railroad train. The speedometer provides both a continuously updated preferably digital reading of vehicle speed and an odometer reading of accumulative mileage.
The prior art discloses radar speedometers for displaying vehicle speed. However, these prior art devices are characterized by certain problems. For example, some of these devices are rather complex and expensive to fabricate. Another problem that is inherent in prior art systems, is brought about by the presence of spurious noise signals which many times cause false counts.
In a prior art system such as the one shown in U.S. Pat. No. 3,833,906 the antenna is typically maintained at a 45.degree. angle relative to the ground. If this angle changes for any reason during use of the device, the output reading is improper, being either higher or lower than the proper reading.
It is also known in the prior art that signal pulses are many times lost and although attempts have been made to provide for replacement of these lost pulses, the techniques employed have not been completely successful.
Accordingly, one object of the present invention is to provide an improved radar speedometer for use on land vehicles.
Another object of the present invention is to provide a radar speedometer that is not unduly complex in construction and that can be easily installed in any existing vehicle.
A further object of the present invention is to provide novel noise rejection means for preventing false counts due to noise signals.
Still another object of the present invention is to provide a signal stabilization means which is responsive to the frequency of the incoming signal for essentially replacing lost signal pulses.
Another object of the present invention is to provide for calibrating both the speedometer and odometer output readings as a function of antenna angle.